Four different sealants (Delton R, Kerr R, Nuva-Seal R and Nuva-Cote R) will be evaluated for wear in vivo over a 2 year period. The subjects will be between 12 and 16 years of age. Only unrestored, caries-free first and second maxillary premolars and molars, and mandibular second premolars and first and second molars will be used. Impressions will be taken of the study teeth prior to, and immediatedly after, sealant application, and after 1, 6, 12, 18 and 24 months. Tooth replica models will be constructed from all impressions. Silver copings will be made from the post-sealant dies using an electroplating technique. The volumetric assessment of wear will be done according to the method previously reported on by the investigators (J. Pros. Dent., 40: 531-533, Nov. 1978). The wear profile will be evaluated by sectioning the silver copings bucco-lingually with the post sealant recall dies in place. Each half will subsequently be photographed and tracings of these photographs will be superimposed to give a composite drawing of the profile changes during the two year study period. Scanning electron microscopy of selected tooth replica models will also be taken to evaluate the amount of sealant retained. Two teeth will be selected from each of three sealant retention levels (clinically intact, partially lost and clinically undetectable) from each of the four treatment groups for a total of 36 teeth. The results from the volumetric assessment will be analyzed statistically by performing five-way analysis of variance with repeated measures in time.